Background. Enriched environment (EE) can protect the brain against damages caused by an ischemic stroke; however, the underlying mechanism remains elusive. Autophagy and mitochondria quality control are instrumental in the pathogenesis of ischemic stroke. In this study, we investigated whether and how autophagy and mitochondria quality control contribute to the protective effect of EE in the acute phase of cerebral ischemiareperfusion injury. Methods. We exposed transient middle cerebral artery occlusion (tMCAO) mice to EE or standard condition (SC) for 7 days and then studied them for neurological deficits, autophagy and inflammation-related proteins, and mitochondrial morphology and function. Results. Compared to tMCAO mice in the SC group, those in the EE group showed fewer neurological deficits, relatively downregulated inflammation, higher LC3 expression, higher mitochondrial Parkin levels, higher mitochondrial fission factor dynamin-related protein-1 (Drp1) levels, lower p62 expression, and lower autophagy inhibitor mTOR expression. Furthermore, we found that the EE group showed a higher number of mitophagosomes and normal mitochondria, fewer mitolysosomes, and relatively increased mitochondrial membrane potential. Conclusion. These results suggested that EE enhances autophagy flux by inhibiting mTOR and enhances mitophagy flux via recruiting Drp1 and Parkin to eliminate dysfunctional mitochondria, which in turn inhibits inflammation and alleviates neurological deficits. Limitations. The specific mechanisms through which EE promotes autophagy and mitophagy and the signaling pathways that link them with inflammation need further study.

Fasudil, a Rho-associated protein kinase (ROCK) inhibitor, has a protective effect on the central nervous system. In addition, environmental enrichment is a promising technique for inducing the recovery of motor impairments in ischemic stroke models. The present study aimed to explore whether environmental enrichment combined with fasudil can facilitate motor function recovery and induce cortical axonal regeneration after stroke. First, a mouse model of ischemic cerebral stroke was established by photochemical embolization of the left sensorimotor cortex. Fasudil solution (10 mg/kg per day) was injected intraperitoneally for 21 days after the photothrombotic stroke. An environmental enrichment intervention was performed on days 7-21 after the photothrombotic stroke. The results revealed that environmental enrichment combined with fasudil improved motor function, increased growth-associated protein 43 expression in the infarcted cerebral cortex, promoted axonal regeneration on the contralateral side, and downregulated ROCK, p-LIM domain kinase (LIMK)1, and p-cofilin expression. The combined intervention was superior to monotherapy. These findings suggest that environmental enrichment combined with fasudil treatment promotes motor recovery after stroke, at least partly by stimulating axonal regeneration. The underlying mechanism might involve ROCK/LIMK1/cofilin pathway regulation. This study was approved by the Institutional Animal Care and Use Committee of Fudan University, China (approval No. 20160858A232) on February 24, 2016.

Stroke seriously affects human health. Many studies have shown that enriched environment (EE) can promote functional recovery after stroke, but the intrinsic mechanisms remain unclear. In order to study the internal mechanisms of EE involved in functional recovery after ischemic stroke and which mechanism plays a leading role in the recovery of limb function after cerebral infarction, key proteins potentially involved in neuronal protection and synaptic remodeling in the ischemic penumbra have been investigated. In this study, adult C57BL/6 mice after permanent middle cerebral artery occlusion (pMCAO) were assigned to the EE and standard housing (SH) groups 3 days after operation. The EE house was spacious that contained a large variety of small toys; the SH was a normal sized cage. Sham‐operated mice without artery occlusion were housed under standard conditions and were fed a normal diet. On days 3, 7, 14, and 21, postoperative motor functional recovery was tested using the modified neurological severity score (mNSS) and the Rotarod test. The expression of B‐cell lymphoma‐2 (Bcl‐2), Bcl‐2‐associated X protein (Bax), growth‐associated protein‐43 (GAP‐43), and synaptophysin (SYN) was examined by western blotting and immunofluorescence staining. The motor functional recovery (based on the mNSS and Rotarod test 3, 7, 14, and 21 days post operation) of mice in the EE group improved significantly compared to the SH group. The expression of GAP‐43 and SYN and the ratio of Bcl‐2/Bax were all upregulated in the EE group compared to the SH group. In addition, we also explored the relationship between neuronal protection and synaptic remodeling in the EE‐mediated recovery of limb function after cerebral infarction by correlation analysis. Correlation analysis showed that compared with the increase of Bcl‐2/Bax ratio, the increased expression of GAP‐43 and SYN was more closely related to the recovery of limb function in ischemic mice. These data support the hypothesis that EE can promote the process of improvement of limb dysfunction induced by ischemic stroke, and this behavior restoration may, via promoting neuroprotection in the ischemic penumbra, be dependent on the regulation of the expression of GAP‐43, SYN, Bcl‐2, and Bax. A limitation of the study was that we only observed several representative key indicators of synaptic remodeling and neuronal apoptosis, without an in‐depth study of the potential mechanisms involved.

Vascular dementia (VaD), attributed to cerebrovascular pathology, is a leading cause of cognitive decline, characterized by memory loss, bradyphrenia, and affective lability, with memory deficits being particularly pronounced. The potential of enriched environment (EE) to ameliorate cognitive impairments by enhancing hippocampal synaptic plasticity, neurogenesis, and white matter remodeling has garnered considerable interest. In this study, we used a rat model for VaD through the procedure of bilateral common carotid artery ligation (BCCAO). We randomly assigned male Sprague-Dawley (SD) rats to three groups: the control sham-operated group (Sham group), the surgery-induced dementia group (BCCAO group), and the surgery-induced dementia group with enriched environment (EE group). The Sham and BCCAO groups were kept under standard lab conditions, whereas the EE group was housed in an enriched setting. Employing a behavioral assay battery, we observed that EE intervention significantly improved the spatial learning and memory performance in the Morris water maze. Subsequent neuromorphological assessments utilizing transmission electron microscopy disclosed an increase in synaptic density and postsynaptic density (PSD) thickness within the hippocampal CA1 region, indicative of structural synaptic modulation. Further probing into the molecular underpinnings revealed that EE upregulated the expression of PSD95, corroborating its role in enhancing cognitive faculties. Additionally, our investigation into the PGC-1α/FNDC5/BDNF pathway demonstrated that EE intervention elevated the expression of these neurotrophic factors, suggesting a mechanistic link to synaptic and cognitive restoration. In summation, our findings elucidate the neurorestorative potential of EE in a preclinical VaD model, presenting a non-pharmacological intervention that modulates synaptic architecture and activates neuroprotective pathways. The observed correlations between synaptic remodeling and cognitive enhancement underscore the therapeutic relevance of EE in VaD, warranting further investigation for clinical applications.

Cerebral ischemia–reperfusion injury triggers mitochondrial dysfunction and oxidative stress, exacerbating neuronal apoptosis. Emerging evidence highlights hydrogen sulfide (H₂S) as a gasotransmitter modulating redox balance, autophagy, and apoptosis. This study investigates the neuroprotective mechanisms of Enriched Environment (EE) against ischemic injury, focusing on mitochondrial dynamics and H₂S-mediated pathways. Using MCAO mice and OGD/R-treated SH-SY5Y neurons, interventions targeting H₂S synthesis, hypoxia-inducible factor 1-alpha (HIF-1α), and mitophagy were implemented. Behavioral, histological, and molecular analyses demonstrated EE significantly improved neurological outcomes, suppressed apoptosis, and attenuated oxidative damage (reduced MDA, elevated MnSOD/glutathione). Mechanistically, EE enhanced mitophagy via dual pathways: canonical PINK1/parkin-mediated mitochondrial clearance, corroborated by transmission electron microscope and LC3B/parkin colocalization, and non-canonical HIF-1α/BNIP3L axis activation. Transcriptomic and Co-immunoprecipitation (Co-IP) data revealed EE upregulated endogenous H₂S biosynthesis post-injury by promoting dopamine-induced calcium influx, which activated calmodulin-dependent signaling to stimulate cystathionine β-synthase/γ-lyase expression. Pharmacological blockade of H₂S synthesis or HIF-1α abolished mitochondrial protection, confirming H₂S as a central mediator. Notably, H₂S exerted antiapoptotic effects by restoring mitochondrial integrity through synergistic mitophagy activation and oxidative stress mitigation. These findings propose a novel neuroprotective cascade: EE-induced dopaminergic signaling potentiates H₂S production, which coordinates PINK1/parkin and HIF-1α/BNIP3L pathways to eliminate dysfunctional mitochondria, thereby preserving neuronal homeostasis. This study elucidates therapeutic potential of EE via H₂S-driven mitochondrial quality control, offering insights for ischemic brain injury intervention.